The present invention relates to a method for stabilizing an oxide-semiconductor interface by using a Group Vb element and to a stabilized semiconductor. In further detail, the invention of the present application provides a method for stabilizing an oxide-semiconductor interface and a stabilized semiconductor, which are useful in highly integrated circuits, ferroelectric materials, ferroelectric memories, etc.
Extensive research and development have been made heretofore on realizing integrated circuits (referred to sometimes hereinafter as xe2x80x9cICsxe2x80x9d) with yet higher degree of integration and on realizing ferroelectric ICs. As a means of implementing such ICs with higher integration and ferroelectric ICs, there is established a method comprising forming an oxide film on the surface of a semiconductor such as a silicon to obtain a semiconductor oxide film.
However, the interface between the semiconductor and the oxide film thus formed by a conventional method is extremely unstable, and hence, various reactions were found to occur as to result in unavoidable problems such as an increase in leak current, a malfunction of capacitors, etc.
The problem of such an unstable oxide/semiconductor interface not only concerns the conventionally known electronic components, but also is a severe problem on realizing ferroelectric memories that are attracting much attention as an ultimate memory structure in near future. No solution of overcoming such an unstable oxide/semiconductor interface is found to present, and this has been the obstacle in implementing a ferroelectric memory. Very recently, however, some methods of stabilizing the oxide/semiconductor interface are being proposed to solve the problem of unstable oxide/semiconductor interface.
Such proposals include, for instance, as shown in FIG. 3, a method for stabilizing the oxide/semiconductor interface, which comprises interposing a stable interface oxide (50) such as Y2O3, MgO, BiSiO3, etc., between a functional oxide (1) such as BaTiO3 or SrTiO3, etc., and the semiconductor (2) such as a Si substrate.
However, in the case of a known method for stabilizing the oxide/semiconductor interface as shown in FIG. 3, an interface layer (a reaction layer) (51), although being thin, was found to be formed between the semiconductor (2) and the interface oxide (50), which unavoidably resulted in a semiconductor with impaired function.
Furthermore, since two types of oxides, namely, the functional oxide (1) and the interface oxide (50), are laminated, there was found another severe problem of causing insufficient exhibition of the intrinsic performance of the functional oxide (1).
Considering the stabilization behavior of the oxide/semiconductor interface in atomic level, the stabilization is realized by the bonding that is formed between the elements constituting the interface oxide (50) and the dangling bonds of the elements constituting the semiconductor (2). For instance, FIG. 4(A) shows schematically a part of the structure of a clean (001) surface of semiconductor Si that is highly reactive, because the outermost surface of the semiconductor Si consists of Si dimers having dangling bonds that are filled with two electrons and those having no electrons. Hence, an interface layer is formed between the semiconductor and the interface oxide as a result.
Furthermore referring to FIG. 4(B), on considering the bonding between the Si dimers (53) in the outermost layer and the Si atoms (52) in the lower layers in the atomic level, it can be understood that the bond is highly stressed by the strain applied thereto. Thus, if seen in atomic level, the bonding between the Si dimers (53) in the outermost layer and the Si atoms (52) in the lower layers easily causes breakage at low temperatures. Hence, theoretically, the oxide/semiconductor interface can be stabilized at super low temperatures. In practice, however, the stabilization of the oxide/semiconductor interface was found to be extremely difficult.
Conclusively, no methods capable of stabilizing the oxide/semiconductor interface independent to temperature while sufficiently exhibiting the performance of the functional oxide without allowing the formation of an interface layer (reaction layer) between a semiconductor and the interface oxide, nor a stabilized semiconductor, are realized to present.
In the light of the aforementioned circumstances, an object of the invention of the present application is to provide a method of stabilizing the oxide/semiconductor interface independent to temperature, which yet sufficiently realizes the performance of the functional oxide without forming an interface layer (reaction layer) between a semiconductor and the interface oxide, and to provide a stabilized semiconductor.
As a means of overcoming the aforementioned problems, the invention of the present application provides, in a first aspect, a method of stabilizing an oxide-semiconductor interface by using a Group Vb element, which comprises supplying an elemental Group Vb element or two or more types of Group VB element to the surface of a semiconductor and growing an oxide on said Group Vb element, thereby stabilizing the interface between the oxide and the semiconductor.
Furthermore, the invention of the present application provides, in a second aspect, a method of stabilizing an oxide-semiconductor interface by using a Group Vb element, wherein the semiconductor is silicon, the Group Vb element is As, and the oxide grown on the Group Vb element is a functional oxide such as CeO2, BaTiO3, PbZrTiO3, or SrTiO3.
Additionally, the invention of the present application provides, in a third aspect, a stabilized semiconductor the oxide-semiconductor interface thereof is stabilized by using a Group Vb element, in which the interface between the oxide and the semiconductor is stabilized by an oxide being grown on the surface of the semiconductor with an elemental Group Vb element or two or more types of Group Vb element being incorporated between them.
That is, the inventors of the present application extensively conducted studies, and, as a result, they have found that, by terminating the surface of the semiconductor with a Group Vb element, a surface structure having extremely low reactivity can be formed at the interface between the oxide and the semiconductor. The present invention has been accomplished based on these findings.